# phpman > man > ss(8)

[SS(8)](https://www.chedong.com/phpMan.php/man/SS/8/markdown)                                  System Manager's Manual                                 [SS(8)](https://www.chedong.com/phpMan.php/man/SS/8/markdown)



## NAME
       ss - another utility to investigate sockets

## SYNOPSIS
       **ss** [_options_] _[_ _FILTER_ _]_

## DESCRIPTION
       **ss**  is  used to dump socket statistics. It allows showing information similar to _netstat_.  It
       can display more TCP and state information than other tools.


## OPTIONS
       When no option is used ss displays a list of open non-listening sockets  (e.g.  TCP/UNIX/UDP)
       that have established connection.

### -h, --help
              Show summary of options.

### -V, --version
              Output version information.

### -H, --no-header
              Suppress header line.

### -O, --oneline
              Print each socket's data on a single line.

### -n, --numeric
              Do  not  try  to resolve service names. Show exact bandwidth values, instead of human-
              readable.

### -r, --resolve
              Try to resolve numeric address/ports.

### -a, --all
              Display both listening and non-listening (for TCP this means established  connections)
              sockets.

### -l, --listening
              Display only listening sockets (these are omitted by default).

### -o, --options
              Show timer information. For TCP protocol, the output format is:

              timer:(<timer_name>,<expire_time>,<retrans>)

              **<timer**___**name>**
                     the name of the timer, there are five kind of timer names:

                     **on**  : means one of these timers: TCP retrans timer, TCP early retrans timer and
                     tail loss probe timer

                     **keepalive**: tcp keep alive timer

                     **timewait**: timewait stage timer

                     **persist**: zero window probe timer

                     **unknown**: none of the above timers

              **<expire**___**time>**
                     how long time the timer will expire

              **<retrans>**
                     how many times the retransmission occurred

### -e, --extended
              Show detailed socket information. The output format is:

              uid:<uid_number> ino:<inode_number> sk:<cookie>

              **<uid**___**number>**
                     the user id the socket belongs to

              **<inode**___**number>**
                     the socket's inode number in VFS

              **<cookie>**
                     an uuid of the socket

### -m, --memory
              Show socket memory usage. The output format is:

              skmem:(r<rmem_alloc>,rb<rcv_buf>,t<wmem_alloc>,tb<snd_buf>,
                            f<fwd_alloc>,w<wmem_queued>,o<opt_mem>,
                            bl<back_log>,d<sock_drop>)

              **<rmem**___**alloc>**
                     the memory allocated for receiving packet

              **<rcv**___**buf>**
                     the total memory can be allocated for receiving packet

              **<wmem**___**alloc>**
                     the memory used for sending packet (which has been sent to layer 3)

              **<snd**___**buf>**
                     the total memory can be allocated for sending packet

              **<fwd**___**alloc>**
                     the memory allocated by the socket as cache, but not used for receiving/sending
                     packet  yet.  If  need  memory to send/receive packet, the memory in this cache
                     will be used before allocate additional memory.

              **<wmem**___**queued>**
                     The memory allocated for sending packet (which has not been sent to layer 3)

              **<ropt**___**mem>**
                     The memory used for storing socket option, e.g., the key for TCP MD5 signature

              **<back**___**log>**
                     The memory used for the sk backlog queue. On a process context, if the  process
                     is  receiving  packet, and a new packet is received, it will be put into the sk
                     backlog queue, so it can be received by the process immediately

              **<sock**___**drop>**
                     the number of packets dropped before they are de-multiplexed into the socket

### -p, --processes
              Show process using socket.

### -i, --info
              Show internal TCP information. Below fields may appear:

              **ts**     show string "ts" if the timestamp option is set

              **sack**   show string "sack" if the sack option is set

              **ecn**    show string "ecn" if the explicit congestion notification option is set

              **ecnseen**
                     show string "ecnseen" if the saw ecn flag is found in received packets

              **fastopen**
                     show string "fastopen" if the fastopen option is set

              **cong**___**alg**
                     the congestion algorithm name, the default congestion algorithm is "cubic"

              **wscale:<snd**___**wscale>:<rcv**___**wscale>**
                     if window scale option is used, this field shows the send scale factor and  re‐
                     ceive scale factor

              **rto:<icsk**___**rto>**
                     tcp re-transmission timeout value, the unit is millisecond

              **backoff:<icsk**___**backoff>**
                     used  for exponential backoff re-transmission, the actual re-transmission time‐
                     out value is icsk_rto << icsk_backoff

              **rtt:<rtt>/<rttvar>**
                     rtt is the average round trip time, rttvar is the mean deviation of rtt,  their
                     units are millisecond

              **ato:<ato>**
                     ack timeout, unit is millisecond, used for delay ack mode

              **mss:<mss>**
                     max segment size

              **cwnd:<cwnd>**
                     congestion window size

              **pmtu:<pmtu>**
                     path MTU value

              **ssthresh:<ssthresh>**
                     tcp congestion window slow start threshold

              **bytes**___**acked:<bytes**___**acked>**
                     bytes acked

              **bytes**___**received:<bytes**___**received>**
                     bytes received

              **segs**___**out:<segs**___**out>**
                     segments sent out

              **segs**___**in:<segs**___**in>**
                     segments received

              **send** **<send**___**bps>bps**
                     egress bps

              **lastsnd:<lastsnd>**
                     how long time since the last packet sent, the unit is millisecond

              **lastrcv:<lastrcv>**
                     how long time since the last packet received, the unit is millisecond

              **lastack:<lastack>**
                     how long time since the last ack received, the unit is millisecond

              **pacing**___**rate** **<pacing**___**rate>bps/<max**___**pacing**___**rate>bps**
                     the pacing rate and max pacing rate

              **rcv**___**space:<rcv**___**space>**
                     a helper variable for TCP internal auto tuning socket receive buffer

              **tcp-ulp-mptcp**  **flags:[MmBbJjecv]**  **token:<rem**___**token(rem**___**id)/loc**___**token(loc**___**id)>** **seq:<sn>**
              **sfseq:<ssn>** **ssnoff:<off>** **maplen:<maplen>**
                     MPTCP subflow information

       **--tos**  Show ToS and priority information. Below fields may appear:

              **tos**    IPv4 Type-of-Service byte

              **tclass** IPv6 Traffic Class byte

              **class**___**id**
                     Class id set by net_cls cgroup. If class is zero this  shows  priority  set  by
                     SO_PRIORITY.

### --cgroup
              Show cgroup information. Below fields may appear:

              **cgroup** Cgroup v2 pathname. This pathname is relative to the mount point of the hierar‐
                     chy.

### -K, --kill
              Attempts to forcibly close sockets. This option displays sockets that are successfully
              closed  and  silently  skips sockets that the kernel does not support closing. It sup‐
              ports IPv4 and IPv6 sockets only.

### -s, --summary
              Print summary statistics. This option does not parse socket  lists  obtaining  summary
              from  various  sources.  It  is  useful when amount of sockets is so huge that parsing
              /proc/net/tcp is painful.

### -E, --events
              Continually display sockets as they are destroyed

### -Z, --context
              As the **-p** option but also shows process security context.

              For [**netlink**(7)](https://www.chedong.com/phpMan.php/man/netlink/7/markdown) sockets the initiating process context is displayed as follows:

                     1.  If valid pid show the process context.

                     2.  If destination is kernel (pid = 0) show kernel initial context.

                     3.  If a unique identifier has been allocated by the kernel  or  netlink  user,
                         show  context as "unavailable". This will generally indicate that a process
                         has more than one netlink socket active.

### -z, --contexts
              As the **-Z** option but also shows the socket context. The socket context is  taken  from
              the  associated inode and is not the actual socket context held by the kernel. Sockets
              are typically labeled with the context of the creating process,  however  the  context
              shown will reflect any policy role, type and/or range transition rules applied, and is
              therefore a useful reference.

### -N NSNAME, --net=NSNAME
              Switch to the specified network namespace name.

### -b, --bpf
              Show socket classic BPF filters (only administrators are allowed to get these informa‐
              tion).

### -4, --ipv4
              Display only IP version 4 sockets (alias for -f inet).

### -6, --ipv6
              Display only IP version 6 sockets (alias for -f inet6).

### -0, --packet
              Display PACKET sockets (alias for -f link).

### -t, --tcp
              Display TCP sockets.

### -u, --udp
              Display UDP sockets.

### -d, --dccp
              Display DCCP sockets.

### -w, --raw
              Display RAW sockets.

### -x, --unix
              Display Unix domain sockets (alias for -f unix).

### -S, --sctp
              Display SCTP sockets.

### --vsock
              Display vsock sockets (alias for -f vsock).

       **--xdp**  Display XDP sockets (alias for -f xdp).

### --inet-sockopt
              Display inet socket options.

### -f FAMILY, --family=FAMILY
              Display sockets of type FAMILY.  Currently the following families are supported: unix,
              inet, inet6, link, netlink, vsock, xdp.

### -A QUERY, --query=QUERY, --socket=QUERY
              List of socket tables to dump, separated by commas. The following identifiers are  un‐
              derstood:  all,  inet,  tcp, udp, raw, unix, packet, netlink, unix_dgram, unix_stream,
              unix_seqpacket, packet_raw, packet_dgram, dccp, sctp, vsock_stream,  vsock_dgram,  xdp
              Any item in the list may optionally be prefixed by an exclamation mark (**!**)  to exclude
              that socket table from being dumped.

### -D FILE, --diag=FILE
              Do not display anything, just dump raw information about TCP sockets to FILE after ap‐
              plying filters. If FILE is - stdout is used.

### -F FILE, --filter=FILE
              Read  filter information from FILE.  Each line of FILE is interpreted like single com‐
              mand line option. If FILE is - stdin is used.

### FILTER := [ state STATE-FILTER ] [ EXPRESSION ]
              Please take a look at the official documentation for details regarding filters.


## STATE-FILTER
       **STATE-FILTER** allows to construct arbitrary set of states to match. Its syntax is sequence  of
       keywords state and exclude followed by identifier of state.

       Available identifiers are:

              All  standard  TCP  states:  **established**,  **syn-sent**, **syn-recv**, **fin-wait-1**, **fin-wait-2**,
              **time-wait**, **closed**, **close-wait**, **last-ack**, **listening** and **closing.**

              **all** - for all the states

              **connected** - all the states except for **listening** and **closed**

              **synchronized** - all the **connected** states except for **syn-sent**

              **bucket** - states, which are maintained as minisockets, i.e.  **time-wait** and **syn-recv**

              **big** - opposite to **bucket**


## EXPRESSION
       **EXPRESSION** allows filtering based on specific criteria.  **EXPRESSION** consists of a  series  of
       predicates  combined  by  boolean  operators.  The  possible operators in increasing order of
       precedence are **or** (or | or ||), **and** (or & or &&), and **not** (or !). If no operator  is  between
       consecutive  predicates,  an  implicit **and** operator is assumed. Subexpressions can be grouped
       with "(" and ")".

       The following predicates are supported:


### {dst|src} [=] HOST
              Test if the destination or source matches HOST. See HOST SYNTAX for details.

### {dport|sport} [OP] [FAMILY:]:PORT
              Compare the destination or source port to PORT. OP can be any of "<", "<=", "=", "!=",
              ">="  and  ">". Following normal arithmetic rules. FAMILY and PORT are as described in
              HOST SYNTAX below.

### dev [=|!=] DEVICE
              Match based on the device the connection uses. DEVICE can either be a device  name  or
              the index of the interface.

### fwmark [=|!=] MASK
              Matches  based  on  the fwmark value for the connection. This can either be a specific
              mark value or a mark value followed by a "/" and a bitmask of which bits to use in the
              comparison.  For example "fwmark = 0x01/0x03" would match if the two least significant
              bits of the fwmark were 0x01.

### cgroup [=|!=] PATH
              Match if the connection is part of a cgroup at the given path.

### autobound
              Match if the port or path of the source address was  automatically  allocated  (rather
              than explicitly specified).

       Most  operators have aliases. If no operator is supplied "=" is assumed.  Each of the follow‐
       ing groups of operators are all equivalent:

              • = == eq

              • != ne neq

              • > gt

              • < lt

              • >= ge geq

              • <= le leq

              • ! not

              • | || or

              • & && and

## HOST SYNTAX
       The general host syntax is [FAMILY:]ADDRESS[:PORT].

       FAMILY must be one of the families supported by the -f option. If not given  it  defaults  to
       the  family given with the -f option, and if that is also missing, will assume either inet or
       inet6. Note that all host conditions in the expression should either all be the  same  family
       or be only inet and inet6. If there is some other mixture of families, the results will prob‐
       ably be unexpected.

       The form of ADDRESS and PORT depends on the family used. "*" can be used as  a  wildcard  for
       either the address or port. The details for each family are as follows:

       **unix**   ADDRESS  is  a  glob  pattern (see [**fnmatch**(3)](https://www.chedong.com/phpMan.php/man/fnmatch/3/markdown)) that will be matched case-insensitively
              against the unix socket's address. Both path and abstract names  are  supported.  Unix
              addresses do not support a port, and "*" cannot be used as a wildcard.

       **link**   ADDRESS  is the case-insensitive name of an Ethernet protocol to match. PORT is either
              a device name or a device index for the desired link device, as seen in the output  of
              ip link.

### netlink
              ADDRESS   is   a   descriptor  of  the  netlink  family.  Possible  values  come  from
              /etc/iproute2/nl_protos. PORT is the port id of the socket, which is usually the  same
              as the owning process id. The value "kernel" can be used to represent the kernel (port
              id of 0).

       **vsock**  ADDRESS is an integer representing the CID address, and PORT is the port.

       **inet** and **inet6**
              ADDRESS is an ip address (either v4 or v6 depending on the family) or a  DNS  hostname
              that  resolves  to  an ip address of the required version. An ipv6 address must be en‐
              closed in "[" and "]" to disambiguate the port separator. The address may additionally
              have  a prefix length given in CIDR notation (a slash followed by the prefix length in
              bits). PORT is either the numerical socket port, or the service name for the  port  to
              match.


## USAGE EXAMPLES
### ss -t -a
              Display all TCP sockets.

### ss -t -a -Z
              Display all TCP sockets with process SELinux security contexts.

### ss -u -a
              Display all UDP sockets.

### ss -o state established '( dport = :ssh or sport = :ssh )'
              Display all established ssh connections.

       **ss** **-x** **src** **/tmp/.X11-unix/***
              Find all local processes connected to X server.

### ss -o state fin-wait-1 '( sport = :http or sport = :https )' dst 193.233.7/24
              List  all  the  tcp sockets in state FIN-WAIT-1 for our apache to network 193.233.7/24
              and look at their timers.

### ss -a -A 'all,!tcp'
              List sockets in all states from all socket tables but TCP.

## SEE ALSO
       [**ip**(8)](https://www.chedong.com/phpMan.php/man/ip/8/markdown),
       **RFC** 793 - <https://tools.ietf.org/rfc/rfc793.txt> (TCP states)


## AUTHOR
       _ss_ was written by Alexey Kuznetsov, <<kuznet@ms2.inr.ac.ru>>.

       This manual page was written by Michael Prokop <<mika@grml.org>> for the  Debian  project  (but
       may be used by others).



                                                                                               [SS(8)](https://www.chedong.com/phpMan.php/man/SS/8/markdown)